This invention relates in general to an improved film cassette holder which includes means whereby selective portions of the film are to be exposed at different times so that multiple images are recorded on a single sheet of film. The film is typically larger than the camera back. The invention is primarily for use with imaging systems such as oscilloscope cameras which produce hard copies of soft information produced on cathode ray tubes by image formation systems used primarily in medical applications.
Various imaging systems have been used to produce images on a cathode ray tube (CRT) where it is desired to produce permanent or "hard" records of the images. Conventionally, this is done through the use of an oscilloscope camera and the addition of suitable electronics to the oscilloscope so that a large portion of the cathode ray tube is blank while the image of interest, properly sized, is produced on a specific area thereof. Later images are produced in the previously blanked areas of the CRT so that multiple images are ultimately exposed on a single photographic record. The electronics required to produce the image shifting, sizing, and blanking are relatively complex, expensive, and difficult to maintain. Such complex devices must be installed by specialized service engineers, and involved special calibration and problems of drifting from calibration. In addition CRT's have an inherent resolution limitation, so that regardless of the manner in which optical enlargement of the CRT image is accomplished before recordation on the file, lesser-resolution images as the result of sizing are the result. In some instances these disadvantages have been recognized and corrections attempted, usually by providing an extremely high resolution oscilloscope or other means which substantially increase the cost of an imaging system.
Another method commonly used to produce multiple hard images is to utilize a camera which produces one image per piece of film, such as those oscilloscope cameras produced by the Polaroid Corporation. This is disadvantageous whether or not the self-developing film produced by the Polaroid Corporation is used, since multiple pictures each having a single image thereon are always more expensive than a single larger film having multiple images. In the case of self-developing films, the desired wide variety of film sensitivity, contrast, resolution, and other characteristics is not available, so that the imaging system is not as versatile as it otherwise might be.
In a camera system for recording multiple images on a single sheet of film, a degree of automation is desirable to prevent double exposures, to identify positively and without error the different images in a sequence, and to save time, particularly in medical applications. Among the desirable features are automatic transport or positioning of the film in a predetermined sequence upon successive operation of a key or footswitch, and automatic transport or positioning of the film in timed sequence, requiring only the operation of a switch to initiate the sequence.